1. Field of the Invention
This invention relates to work supports for vacuum electric furnaces for support of work wherein case formation in ferrous metals is provided by glow discharge on the work piece in the furnace.
2. Brief Description of the Prior Art
The process of case formation has been previously described in American Society for Metals, Metals Handbook, Vol. 2, commencing at p. 677, wherein the carburization of a surface of a ferrous work piece or ion nitriding of the surface of a work piece provides a case which may be hardened as the case is formed or which may subsequently be hardened is described.
Examples of ion nitriding by electrical discharge in a chamber of a nitrogen containing gas are shown in the U.S. Pat. Nos. to Egan, No. 1,837,256, Berghaus et al., 2,837,654, Keller, 3,761,370 and Jones et al., 3,437,784 and 3,650,930.
The prior systems were particularly subject to arcing if the power input is high, which materially decreased the effectiveness of the process.
In the U.S. Patent to Jones et al., U.S. Pat. No. 3,437,784, a power supply is shown which is intended to limit arcing by limiting the current.
In utilizing glow discharge for surface treatment in case formation, the sputtered material generated at the work piece in the previously available equipment tended to build up on the work supports causing arcing and shorting out of the electrical system.
The work support of our invention does not suffer from the problems encountered in previously available structures and has positive advantages.